Polish authorities say the logging operations are legal and necessary to protect against wood-boring insects.
Environmental activists in Poland have complained about the resumption of logging in a protected forest.
NGOs said that trees are being cut down again in Bialowieza, Europe's last primeval forest in eastern Poland.
But Poland's national forest administration has dismissed the complaint and says that it is acting legally.
The Bialowieza forest is a UNESCO World Heritage site and has also been classified by the European Union as a Natura 2000 area.
The Polish government felled a large number of trees - some over 100 years old - in 2016, claiming that it wanted to combat the spread of wood-boring insects.
In 2018, the Court of Justice of the EU ruled that the logging operations violated EU law and ordered Poland to suspend them.
But earlier this year, the Polish government announced that logging in the forest was set to resume.
"The work carried out has nothing to do with nature protection and conservation measures," several environmental organisations wrote in a statement on Tuesday.
"On the contrary, it devastates the nature of the forest and is carried out against the norms and regulations."
The statement - signed by groups including Greenpeace and the NGO Wild Poland - has urged Polish authorities to suspend logging again.
Ecologists have also said that the use of heavy machinery in the forest will destroy soil and vegetation.
According to the Browsk forest district, the latest operations aim to "maintain the continuity of the forest" and are taking place outside the UNESCO protection zone.
"[We want] to achieve a healthy and stable young generation of the forest in the most beneficial way for a given species," the authority said.